Transcript Electric fields - Bibb County Schools

ELECTRICITY
What would life be like without electricity?
List 4 things that you would miss the most:
1) ______________________________
2) ______________________________
3) ______________________________
4)
______________________________
Positive and Negative Charge
• atoms have protons (positive)
and electrons
(negative); neutrons are
neutral
• when objects have an excess
of electrons, they become
negatively charged
Opposites attract
Objects with the same
charge repel
Diagram of an Atom
Protons and Neutrons are in the center
Electrons orbit around the outside
-- these are SUBatomic particles
Bohr model of the atom
Label the protons,
neutrons, electrons, and
the nucleus
1. Name the six types of
quarks:
2. What is another particle that is smaller than a subatomic
particle? (starts with the letter L)
3. What is meant by DUAL NATURE of particles?
Static electricity occurs when
electrons transfer to your
clothes or hair and give them
a charge. When you touch
something, the charge is
released, causing a "jolt"
Each hair is negatively
charged and repels other
hairs.
Or balloons stick to the cat
Electric fields surround every charge and can act
upon other objects (even without touching them)
The force created by this field can either
attract
or
repel
Conductor - material in which electrons
can flow freely
Ex. Metals, such as copper
Insulator - electrons do not move easily
through
Ex. plastic, rubber
1. What happens when
warm air collides with cold
air?
2. Humans are good
conductors because they
contain ___________
Lightning Gallery at
http://environment.nationalgeographic.com/
environment/photos/lightning-cloud-ground/
3. Name one thing you can
do to decrease your
chances of being struck by
lightning?
4. What is a stepped
leader?
What is Grounding?
Buildings often install lightning rods, which provide a
path for electrons to take to the earth, bypassing the
building and sensitive electric equipment
What Is Electric Current?
- net movement of electric charges (electrons)
in a single direction
- measured in amperes
This diagram shows a simple LED driver circuit. When the
battery is connected the positive end of the battery pulls
electrons from the negative end of the battery and through
the circuit. This circuit has three basic properties: voltage,
current, and resistance.
What Is a Voltage Difference?
- the force that causes
electrons to flow
- electric charge flows from a
higher voltage to a lower
voltage
Circuit = a closed path that electric
current follows
This flow of electrons can power things
like light bulbs
Resistance = tendency for material to
oppose the flow of electrons
-- electric current loses energy as it flows
-- resistance is measured in OHMS
* Copper has a low
resistance, hence it is
used for household wiring
and other electronics
STOP AND THINK
1. A positively charged subatomic particle is ____
negatively charged subatomic particle is ____
2. Amperes are used to measure _________
3. A closed path that electrons (current) can flow through is a:
4. Materials that current can flow through easily are called:
5. OHMS are used to measure the __________ of a circuit.
As the length of a
wire increases, so
does its resistance
As the wire becomes
thinner, its resistance
increases
the thin wire in a tungsten
light bulb glows due to
this resistance
Ohm's Law -- the current (I) in a circuit
equals the voltage difference (V)
divided by resistance (R)
Quick Calculations:
1. What is the current of a circuit with a
voltage difference of 20 volts and a resistance
of 10 ohms.
2. What is the Voltage difference in a circuit
with a resistance of 11 ohms, and a current of
2 amperes.
1. What is the center of an atom called?
2. Electrons are attracted to _________
3. Electrons move from the ___ to the ___ side of a battery.
4. What is the most common metal used in wiring?
5. How many volts are in an AA battery? ______
6. How many volts are in a wall outlet?
7. A device used to turn electricity on and off is a _______
8. In which type of circuit can you turn a light off and the other
will stay on? [ series / parallel ]
Circuits
How many electrical devices can you see in this room? Name
2.
Circuits have:
1) source of voltage difference (battery or outlet)
2) device that uses the energy (light)
3) conductors (wires) form a closed path to device
Series Circuit
Example: A string of christmas lights, when one light burns out,
no lights will work. Why? Because that burned out bulb breaks
the circuit to all the bulbs.
Each bulb along the
path shares the
voltage, so the bulbs
may appear dim.
Parallel Circuits
Series circuits aren't a good way to wire a
house. If you turned off one light, then all
the lights would go out.
Parallel circuits contain two or more
branches
Disadvantage: Even when you turn a light
off, current continues to flow through the
system.
This is why you shouldn't stick a fork in an
electric socket!
A switch can break a circuit
And turn a device on or off
Would this switch
still work?
Identify the type of circuit:
______________________
______________________
What is a fuse?
Fuses contain a tiny
piece of metal that
melts if the current gets
too high - this breaks
the circuit.
Too many appliances
on in one room can
overload the circuit and
blow a fuse.
Where does electricity come from?
Most electricity comes from converting heat energy into
electrical energy - burning fossil fuels such as coal and natural
gas.
Some electricity is generated from dams, and nuclear reactors
How do dams generate electricity?
As water flows
through the dam it
spins turbines, which
will create electricity.
These are referred to
as:
HYDROELECTRIC
DAMS
How are dams built?
How do they hold all that water back?
What happens when dams fail?
Cost of Electricity
1) Most companies charge by the
amount of energy used
2) This is measured in kilowatt hours
(kWh)
3) Each light bulb in your house
costs money to leave on!
4) Meters outside your house
measure how much energy is used
Check out:
http://www.energyeducation.tx.gov/
What is the difference between
alternating current and direct current?
Check out
http://www.pbs.org/wgbh/amex/edison/sf
eature/acdc.htmlhttp://www.pbs.org/wgbh
/amex/edison/sfeature/acdc.html
AC = alternating current
DC = direct current
Direct Current is found in simple
circuits like a battery powered
flashlight.
Alternating Current
The direction of current flowing in
a circuit is constantly being
reversed back and forth. This is
done with any type of AC
current/voltage source.
AC power is used in homes and
business. It's cheaper and easier
to make devices for AC power,
and you can easily increase and
decrease the current.
QUIZ TIME
1. What happens when an object has an excess number of
electrons?
2. Name something that is a conductor:
3. What unit is electric current measured in?
4. What unit is electric energy measured in (think power bill)?
5. The force that causes electrons to flow is the ____________
difference.
6. Is the image showing a
parallel or series circuit?
7. Where does the
electricity come from that
powers your house?
8. What causes a fuse to
be blown?
9. _________ Law can be
used to calculate voltage.
10. Resistance is the tendency
for ____________ to oppose
the flow of ____________.